shot peening

r44flyer · Post by **r44flyer** » Wed Mar 02, 2005 12:48 pm

hi all....

just for anyone's interest really. got a quote recently for shot peening a set of conrods from a company called IST.

Â£34 +VAT for a set of 4.

A recommended process if you're keeping standard rods, perhaps with forged pistons, and increasing power. Basically, it increases surface tension in the metal thus increases its stress tolerance. And not a bad price really.

Personal email address for 'man in charge of shot peening' available on request! :wink:

regards

Jim

Si · Post by Si » Wed Mar 02, 2005 2:18 pm

Shot peening won't help under compression though which is the T16s weakness.

george_chick · Post by **george_chick** » Wed Mar 02, 2005 2:57 pm

For those wandering past, who like me aren't too sure what this is about.

Shot peening is a method used to cold work the surface of metal objects to improve fatigue life, strength, operation and corrosion resistance. The process compresses the surface of the part by bombarding it with hard spherical particals such as steel shot or glass bead, resulting in a compressed layer of metal that gives the object a tough skin. The result is a part that is more reliable and resistant to cyclic fatigue. Failures generally begin at the surface defects or stress concentrations known as stress raisers.

r44flyer · Post by **r44flyer** » Wed Mar 02, 2005 3:09 pm

Turbo Si wrote:Shot peening won't help under compression though which is the T16s weakness.

but it will help to stop the rods fracturing though surely? and if it increases strength then that helps against compressive forces doesn't it?

Jonny 5 · Post by **Jonny 5** » Wed Mar 02, 2005 3:25 pm

Rods rarely fracture, they bend and the resulting reduction in cylinder pressure stops em bending further, or the rod bolt lets go and the crank on the next stroke will send them thorugh the block wall :oops:

r44flyer · Post by **r44flyer** » Wed Mar 02, 2005 3:55 pm

so it shot peening rods a waste of time then?

Jonny 5 · Post by **Jonny 5** » Wed Mar 02, 2005 3:58 pm

No not at all.

r44flyer · Post by **r44flyer** » Wed Mar 02, 2005 4:04 pm

well at under Â£40 it can't hurt to get it done can it. :wink:

Grant620 · Post by **Grant620** » Wed Mar 02, 2005 6:54 pm

I agree it can't hurt, but I can't see the need personally as I've never seen a rod damaged in any way except bent.

bgunn · Post by **bgunn** » Wed Mar 02, 2005 10:23 pm

Watch out when you shot peen the rods too - stresses in the rods may be relieved which cause the rods to bend and need to be straightened..

Or so David Vizard says

Brian.

Chris220SDi · Post by **Chris220SDi** » Wed Mar 02, 2005 11:40 pm

bgunn wrote:Watch out when you shot peen the rods too - stresses in the rods may be relieved which cause the rods to bend and need to be straightened..

...but surely better to know during / after the shot peening process rather than at 6000rpm in your newly built engine

Si · Post by Si » Thu Mar 03, 2005 9:36 am

Chris220SDi wrote:
bgunn wrote:Watch out when you shot peen the rods too - stresses in the rods may be relieved which cause the rods to bend and need to be straightened..

...but surely better to know during / after the shot peening process rather than at 6000rpm in your newly built engine

Shot peening won't increase compressive strength at all though, so they won't be less likely to bend under compressive loads.

It will increase tensile strength of the rod though

Grant620 · Post by **Grant620** » Thu Mar 03, 2005 11:33 pm

Which in a blown engine is neither here nor there IMO.

Chris220SDi · Post by **Chris220SDi** » Sat Mar 05, 2005 12:49 am

Turbo Si wrote:Shot peening won't increase compressive strength at all though, so they won't be less likely to bend under compressive loads.

It will increase tensile strength of the rod though

Let me just get this straight Si...

...you said that above - then r44flyer asked if shot peening was a waste of time, Jonny said "no, not at all", and you've just said "it will increase the tensile strength" so erm you and Jonyn have both said that shot peening is worth doing.

So, if its not worth doing to protect the rest of the engine while its running? Why is it worth doing?

...your trying to play with my head arent you? its a conspiricy I tell thee!

Si · Post by Si » Sat Mar 05, 2005 1:25 am

A t16 rod will fail under boost.

Shot peening itself is worthwhile, however if you are doing it only to increase the power capablility of the standard rod (ie stop it bending) then shot peening won't help.

The Shot peening process involves firing 'shots' at the conrod out surface, these dent the metal and induce compressive loads within the surface of the rod. The help increase the tensile strength of the rod and reduce the chance of cracks forming and propagating though the metal causing a failuer under high tensile loads (High engine speeds)

Shot peening won't help the rods cope with more compression forces though (Engine torque).

Hope this is clearer Fev.

bgunn · Post by **bgunn** » Wed Mar 09, 2005 9:09 pm

Chris220SDi wrote:
bgunn wrote:Watch out when you shot peen the rods too - stresses in the rods may be relieved which cause the rods to bend and need to be straightened..

...but surely better to know during / after the shot peening process rather than at 6000rpm in your newly built engine

No. What I mean is - any stresses that are "sitting" unrelieved in the rod, can be relieved by the shot peening process. These original stresses are placed in the billet of metal during the forging process..

As Si says, they'll bend under compression anyway..

Brian.